Background/Rationale: President Obama and Secretary Shinseki pledged to end homelessness among Veterans by 2015. The U.S. Department of Housing and Urban Development (HUD)-VA Supportive Housing (VASH) program is a prominent element of the VA strategic plan to end Veteran homelessness. HUD-VASH offers vouchers that homeless Veterans use for rental units in their communities, combined with supportive services provided by the VA. As one of the largest initiatives to end Veteran homelessness, the HUD-VASH program distributed approximately 60,000 vouchers to Veterans since 2009. However, 25% of Veterans in HUD-VASH prematurely exit the program each year during the first five years of participation. Objectives: To inform intervention development that can decrease exits from HUD-VASH, we will use the Behavioral Model for Vulnerable Populations for the following specific aims: 1) To describe Veterans with negative exits from HUD-VASH in comparison to Veterans who remain in the program, including predisposing factors [(demographics, housing, illness burden)], enabling factors [(source of care, social support, income, needs that compete with care)], perceived/evaluated needs, and behaviors [(rent payments, adherence to rules of apartment living/case management, use and adherence to health services)]; 2) To identify potentially modifiable predisposing factors [(mental illness, physical illness, and substance use disorders)], enabling factors [(source of care, social support, income, needs that compete with care)], and behaviors [(rent payments, adherence to rules of apartment living/case management, use and adherence to health services)] that are associated with exits from HUD-VASH; and 3) Using qualitative and quantitative methods, to characterize patterns of Veteran experiences and the role of [HUD-VASH services to address enabling factors (regular source of care, social support, employment assistance, ability to negotiate system), unmet needs, and behaviors (rent payments, adherence to rules of apartment living/case management, use and adherence to health care)] among Veterans who exit HUD-VASH in comparison to those who remain in the program. Methods: We will use mixed methods to explore predisposing and enabling factors that interact with perceived/evaluated needs to influence behaviors while housed, along with our core outcome, i.e., [negative] HUD-VASH exits. [Among Veterans who were housed through HUD-VASH at GLA in 2012-2013, we will collect VA administrative and chart review data from n = 150 Veterans with negative exits from HUD-VASH and a group of n = 150 Veterans who remain in the program, with 1:1 matching on age, gender, race/ethnicity, and quarter of the year of housing placement. [Semi-structured, qualitative interviews will be conducted with n = 20 of these Veterans with negative exits from HUD-VASH and n = 20 of these Veterans who are retained in the program, with a focus on HUD-VASH organizational factors. A focus group will be held with frontline GLA HUD-VASH staff and key informant interviews will be conducted with program administrators.] Significance: We know little about Veterans with negative exits from the HUD-VASH program, factors associated with these negative exits or the process and experience of program exit. As the VA rapidly expands HUD-VASH and accelerates its efforts to end homelessness among Veterans [by 2015], it is critical to identify factors associated with exits from HUD-VASH and to use this information to [identify, implement, and evaluate interventions that address modifiable factors that can decrease exits from] this program.